Actuator for disk device

ABSTRACT

In an actuator having a coil disposed between yokes opposing to each other via a specified space, stepped portions are formed at the inner sides of two arms which support the coil, and at the stepped portion are formed through-holes whose diameter is gradually reduced from the bottom to top of the stepped portion. The coil and the arms are joined together by filling the stepped portions and through-holes with a holding member made up of resin. By this configuration, in an actuator used for a disk unit or the like, it is possible to completely secure a coil on a carriage while reducing the unit in thickness.

TECHNICAL FIELD

The present invention relates to an actuator including a carriage havinga head and rocking about a rotary shaft, in a disk unit such as, forexample, a magnetic disk unit.

BACKGROUND ART

In a disk unit such as a magnetic disk unit, a carriage provided with ahead is required to have excellent dynamic characteristics in order toget access to a target track accurately at a high speed.

FIG. 8 is an exploded perspective view of a conventional actuator for adisk unit or the like. FIG. 9 is a plan view of the carriage of FIG. 8,and FIG. 10 shows the X—X section of FIG. 9.

In FIG. 8, magnets 15 are respectively fixed to upper and lower yokes9A, 9B. The yokes 9A, 9B are secured by shafts 16 with a specified spacethere between in a manner such that magnets 15 are opposed to each otherin reverse polarity. A coil 7 is fixed on one end of a carriage 8, andon the other end is located a suspension 6 which supports a head 5 forsignal recording and reproducing. The carriage 8 is supported by arotary shaft (not shown) which is set through bearing 36 so that thecoil 7 is positioned inside the space and able to rotate about therotary shaft. That is, when the coil 7 is supplied with a current, adriving force is generated in the coil 7 according to the Fleming'srule, and thereby, the carriage 8 makes a rocking motion.

In a conventional actuator as described above, examples of configurationwith the coil 7 fixed on the carriage 8 are shown in FIG. 9 and FIG. 10.In these figures, projection 17 for securing the coil 7 is integrallydisposed beforehand at the end of the carriage 8, and the projection 17and the coil 7 are secured by means of holding member 11 made up ofthermoplastic resin.

However, in such conventional configuration, since the coil 7 issupported in a cantilever fashion by the carriage 8, it is not possibleto obtain sufficient strength and rigidity for the installation. As aresult, the resonance frequency of the carriage 8 becomes lowered and itis unable to satisfy the requirement for higher performance of the diskunit.

FIG. 11 and FIG. 12 are perspective views showing other examples ofconfiguration with respect to the carriage 8 and the coil 7. FIG. 11 isa perspective view before assembly of the carriage 8 and the coil 7.FIG. 12 is a perspective view after assembly of the carriage 8 and thecoil 7. In FIG. 12, the portion shaded by black spots is the supportmember 11 made up of resin. FIG. 13 shows the XIII—XIII section of FIG.12. FIG. 14 shows the XIV—XIV section of FIG. 12.

In FIG. 11, a long plate-form projection 13 is formed at the inside ofcoil fitting arm 12A of the carriage 8. Also, there are provided threethrough-holes 14 at the boundary between the bottom portion ofprojection 13 and the arm 12A. The configuration of coil fitting arm 12Bis same as that of the coil fitting arm 12A. The carriage 8 and the coil7 are set in a metallic mold (not shown), and the coil 7 is positionedwith reference to the carriage 8, and holding member 11 made up ofthermoplastic resin is filled therein. Thus, the coil 7 is fixed on thecarriage 8. FIG. 12 is a perspective view of the coil 7 fixed on thecarriage 8. Like the XIII—XIII section of FIG. 12 shown in FIG. 13, thethrough-holes 14 are filled with resin of the holding member 11, andtherefore, the coil 7 will be free from slipping off from the arms 12A,12B in the direction of arrow X in FIG. 12. Also, like the XIV—XIVsection of FIG. 12 shown in FIG. 14, the projection 13 bites into theholding member 11, and the holding member 11 bites into the depression7A of winding of the coil 7 as well. Accordingly, the coil 7 issufficiently held in the direction of arrow Y against the arms 12A, 12B.By such configuration, the portion of fitting the arms 12A, 12B and thecoil 7 can be made nearly equal in thickness to the arms 12A, 12B. Sincethe coil 7 can be disposed between two strong arms 12A and 12B, theresonance frequency will become higher and it is possible to meet therequirement for higher performance of the disk unit.

However, with the recent improvement in performance of disk units, thereis an increasing demand for smaller and thinner disk units. To make thedisk unit further thinner, it is necessary to reduce the entire actuatorless in thickness. For achieving the purpose, it is necessary to makethe yokes 9A, 9B, and magnet 15 thinner, and also to reduce thethickness t see FIG. 14) of arms 12A, 12B and coil 7 as much aspossible. However, if the thickness t of the arm 12A shown in FIG. 14 isreduced, it will become difficult to form the projection 13 in thecenter of arm 12A.

DISCLOSURE OF THE INVENTION

The present invention is intended to solve the above problem, providingan actuator wherein the coil may be secured with a sufficient strengthagainst the carriage even in case the coil fitting arm is reduced inthickness.

The actuator of the present invention has the following configuration.

In this configuration, there are provided a pair of yokes opposing toeach other via the first specified space, a magnet fixed to at least oneof the yokes, and a carriage holding a coil on one end thereof againstthe magnet via the second specified space and rocking about a rotaryshaft; and the carriage comprises two coil fitting arms opposing to eachother having stepped portions respectively formed on the opposingsurfaces and at least one through-hole, piercing from the bottom to thetop of the stepped portion, whose size is larger at the bottom than atthe top thereof, the coil disposed between these two coil fitting arms,and a holding member for securing the coil fitting arms, thethrough-hole and the coil. The holding member is preferable to be formedof a resin-filled block.

By this configuration, since each of the coil fitting arms is providedwith a stepped portion, the coil may be securely fixed on the arms evenin case the arms are reduced in thickness. Also, there are providedthrough-holes at the stepped portion of the arm, and the through-holearea is larger at the bottom of the stepped portion than at the topthereof. Also, resin is filled into these through-holes to secure thecoil, and the resin will free from slipping off from the holes, andthereby, the coil can be completely fixed on both arms.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a magnetic recording unit equipped withan actuator in a first embodiment of the present invention.

FIG. 2 is a perspective view of a carriage and coil before assembly inthe actuator shown in FIG. 1.

FIG. 3 is a perspective view of the carriage and coil after assembly inthe actuator shown in FIG. 1.

FIG. 4 is an enlarged view of encircled portion A in FIG. 2.

FIG. 5 shows the V—V section of FIG. 3.

FIG. 6 shows the VI—VI section of FIG. 3.

FIG. 7 is a sectional view corresponding to FIG. 5 of the firstembodiment in a second embodiment of the present invention.

FIG. 8 is an exploded perspective view of a conventional actuator.

FIG. 9 is a plan view of an essential portion of the actuator shown inFIG. 8.

FIG. 10 shows the X—X section of FIG. 9.

FIG. 11 is a perspective view of an essential portion before assembly inanother example of a conventional actuator.

FIG. 12 is a perspective view of the essential portion after assembly inanother example of a conventional actuator.

FIG. 13 shows the XIII—XIII section of FIG. 12.

FIG. 14 shows the XIV—XIV section of FIG. 12.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

The embodiments of the present invention will be described in thefollowing with reference to the drawings.

(First Embodiment)

FIG. 1 is a perspective view of a magnetic recording unit equipped withan actuator in the first embodiment of the present invention. FIG. 2 isa perspective view of a carriage and coil before assembly in theactuator shown in FIG. 1. FIG. 3 is a perspective view of the carriageand coil after assembly. FIG. 4 is an enlarged view of encircled portionA in FIG. 2. FIG. 5 shows the V—V section of FIG. 3. FIG. 6 shows theVI—VI section of FIG. 3.

In FIG. 1, a magnetic disk unit 1 comprises a magnetic disk 2, a diskclamp 3 to hold the magnetic disk 2, a spindle motor (not shown) torotate the magnetic disk 2, and an actuator 4. The actuator 4 has a coil7 fixed on one end and a suspension 6 fixed on the other end thereof tosupport a magnetic head 5. There are provided a carriage 18, a pair ofyokes 9 disposed so as to be opposed to each other via the firstspecified space, and a magnet (permanent magnet) 15 secured on at leastone inner surface of the yokes 9. In FIG. 1, when the disk unit is notin operation, the suspension 6 is let to move onto lamp 10, showing thatthe magnetic head 5 is taking shelter from above the magnetic disk 2.

Next, the assembly of the coil 7 and the carriage 18 in the firstembodiment will be described. FIG. 2 is a perspective view beforeassembly of both parts, and FIG. 3 is a perspective view after assemblythereof. In FIG. 3, the portion shaded by a number of black spots showsholding member 11 made up of thermoplastic resin to be explained in thefollowing.

As shown in FIG. 2, FIG. 4 and FIG. 5, stepped portion 25 is formed ateach of the inner sides opposing to each other of coil fitting arms 18A,18B of the carriage 18. Three through-holes 24 are formed at the bottomof each stepped portion 25. Each of the through-holes 24, as shown inFIG. 5, is shaped so as to be larger in size at the bottom 25A ofstepped portion 25 than at the top 25B of same, which is identical witha shape (conical trapezoid) obtained, for example, by removing the topof a cone. The carriage 18 and coil 7 shown in FIG. 2 are put into ametallic mold (not shown), then the coil 7 is positioned with respect tothe carriage 18, and after that, thermoplastic resin is filled thereinto secure both parts as shown in FIG. 3. That is, the holding member 11of FIG. 3 is a resin-filled block for securing the arms 18A, 18B, thethrough-holes 24 and the coil 7. In FIG. 3, five holes 27 located insidethe coil 7 are used for insertion of positioning pins disposed in themetallic mold.

As shown in FIG. 5, since the resin of holding member 11 is filled inthe conical trapezoid shaped holes 24, the holding member 11 will befree from slipping off from the arms 18A and 18B. Further, as shown bythe VI—VI section of FIG. 3 shown in FIG. 6, the stepped portion 25 ofarm 18A is joined to the holding member 11, and also the holding member11 is biting into the depression of winding of the coil 7 the same as inthe conventional configuration. Accordingly, the coil 7 is securely heldagainst the arms 18A, 18B. Also, as is apparent in the comparisonbetween the configuration of a conventional example shown in FIG. 13 andthe structure in the first embodiment of the present invention shown inFIG. 5, the reduction in thickness of carriage 18 can be realized in thefirst embodiment. As for the holding member 11, it is also possible toobtain similar effects by using thermosetting resin or time-lapsesetting resin instead of thermoplastic resin.

(Second Embodiment)

FIG. 7 is a sectional view corresponding to FIG. 5 in the firstembodiment in the second embodiment of the present invention. Theactuator in the second embodiment is different from the one in the firstembodiment only with respect to the shape of through-hole.

That is, in the second embodiment, instead of the through-hole 24(conical trapezoid) in the first embodiment, there is provided athrough-hole whose sectional size parallel to the bottom of the steppedportion is gradually reduced up to a specified point from the bottom andis constant up to the top from the specified point.

That is, as shown in FIG. 7, the shape of hole 31 is of conicaltrapezoid in the range from the bottom 25A of stepped portion 25 to themiddle in the direction of thickness of the stepped portion 25, whilethe shape of hole 32 is circular and constant in diameter up to the top25B. In this case, the strength will be further improved because portion34 around the hole 32 at the stepped portion 25 is increased inthickness.

As described above for each of the embodiments, the present invention isable to provide an actuator which is less in thickness and capable ofassuring that the coil is securely fixed on the coil fitting armswithout fear of removal of the coil in the direction vertical to thesurfaces including the coil fitting arms even in case of using coilfitting arms reduced in thickness.

INDUSTRIAL APPLICABILITY

The present invention is an actuator for a disk unit such as a magneticdisk unit, which can meet the requirements for excellent performance andthickness reduction. In a rocking actuator having a coil disposedbetween a pair of yokes opposing to each other via a specified space,stepped portions are formed at the inner sides of two arms which supportthe coil, and at the stepped portions are formed through-holes whosediameter is gradually reduced from the bottom to the top of the steppedportion. The coil may be completely secured on the arms by filling thestepped portions and through-holes with holding member resin. By usingthis configuration, it is possible to provide an actuator which isreduced in thickness and assures excellent strength.

What is claimed is:
 1. An actuator comprising: a pair of yokes opposingeach other, a magnet fixed to at least one of said yokes, a carriagepivotable about a rotary shaft, a coil, and a holding member made ofresin and securing said coil, wherein said carriage includes a pair ofspaced apart coil fitting arms opposing each other, each of said armshaving a stepped portion, the stepped portions of said coil fitting armsfacing each other, and each of said coil fitting arms having at leastone through-hole extending through the respective stepped portion and tothe top of the respective coil fitting arm, said through-hole beingsized larger at the bottom than at the top of said stepped portion,wherein said holding member is disposed between said coil fitting arms,and extends into each through-hole to secure said holding member to saidcarriage, wherein the holding member is configured so that the bottom ofthe stepped portion is substantially flush with the bottom of theholding member, and wherein said stepped portion is formed at each innerside of a pair of coil fitting arms that support said coil, and saidstepped portion and each through-hole are filled with the resin formingsaid holding member.
 2. The actuator of claim 1, wherein said holdingmember is formed of a resin-filled block.
 3. The actuator of claim 1,wherein said stepped portions are respectively formed on the same sidesof said coil fitting arms.
 4. The actuator of claim 1, wherein thesectional size parallel to the bottom of said through-hole is graduallyreduced from the bottom toward the top.
 5. The actuator of claim 1,wherein the sectional area parallel to the bottom of said through-holeis gradually reduced the bottom toward the top.
 6. The actuator of claim1, wherein the sectional size parallel to the bottom of saidthrough-hole is gradually reduced up to a specified point from thebottom and is constant from the specified point up to the top.
 7. Theactuator of claim 1, wherein the sectional area parallel to the bottomof said through-hole is gradually reduced up to a specified point fromthe bottom and is constant from the specified point up to the top. 8.The actuator of claim 1, wherein said through-hole is formed at aboundary portion between said coil fitting arm and said stepped portion.9. The actuator of claim 2, wherein the resin is thermoplastic resin.10. The actuator of claim 2, wherein the resin is thermosetting resin.11. The actuator of claim 2, wherein the resin is time-lapse settingresin.
 12. The actuator of claim 1, wherein the holding member also hasan opposing pair of stepped portions that are complementary to thestepped portions of the coil fitting arms.
 13. An actuator comprising: apair of yokes opposing each other, a magnet fixed to at least one ofsaid yokes, a carriage pivotable about a rotary shaft, a coil, and aholding member formed of a resin-filled block securing said coil,wherein said carriage includes a pair of spaced apart coil fitting armsopposing each other, each of said arms having a stepped portion, thestepped portions of said coil fitting arms facing each other and areformed on the same sides of said coil fitting arms, and each of saidcoil fitting arms having a plurality of through-holes, said through-holebeing sized larger at the bottom than at the top of said steppedportion, wherein said holding member is disposed between said coilfitting arms, and extends into each through-hole to secure said holdingmember to said carriage, wherein the holding member is configured sothat the bottom of the stepped portion is substantially flush with thebottom the holding member, wherein said through-holes extend throughsaid stepped portions and to the top of said coil fitting arms, whereina sectional area parallel to the bottom of the through-holes isgradually reduced from the bottom of the through-hole to a specifiedpoint and is constant up to the top of the through holes from thestepped point, and wherein said stepped portion is formed at each innerside of a pair of coil fitting arms that support said coil, and saidstepped portion each through-hole are filled with the resin forming saidholding member.
 14. The actuator of claim 13, wherein the holding memberalso has an opposing pair of stepped portions that are complementary tothe stepped portions of the coil fitting arms.
 15. The actuator of claim1, wherein positioning the bottom of said holding member flush with thebottom of said stepped portion allows said coil fitting arms to bethinner.
 16. The actuator of claim 13, wherein positioning the bottom ofsaid holding member flush with the bottom of said stepped portion allowssaid coil fitting arms to be thinner.